C program to check if a year is leap year or not

C program to check if a year is leap year or not :

To check if a year is leap year or not, we need to check if it is divisible by 4 or not. A year is leap year if it is divisible by 4 and for century years, if it also divisible by 400. In this example, we will learn how to check if a year is leap year or not in C programming language. Let’s take a look into the algorithm first :

Algorithm to check if a year is leap year or not :

1. Check if it is divisible by 4. If not than it is not a leap year.
2. If divisible by 4, check if it is divisible by 100. If not , it is not a century year, so it is a leap year.
3. If divisible by 100, check if it is divisible by 400 or not. If yes it is a leap year, else not.

List of leap years from 1900 to 2020 are : 1904, 1908, 1912, 1916, 1920, 1924, 1928, 1932, 1936, 1940, 1944, 1948, 1952, 1956, 1960, 1964, 1968, 1972, 1976, 1980, 1984, 1988, 1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020 .
Let’s take a look into the program :

```#include
#define LEAP_YEAR 1
#define NON_LEAP_YEAR 0

int checkLeapYear(int year){
if(year%4 == 0 ){
if(year%100 == 0){
if(year%400 == 0){
return LEAP_YEAR;
}else{
return NON_LEAP_YEAR;
}
}else{
return LEAP_YEAR;
}
}else{
return NON_LEAP_YEAR;
}
}

int main()
{
int year;

printf("Enter a year to check : \n");

scanf("%d",&year);

if(checkLeapYear(year) == LEAP_YEAR){
printf("Entered year is a leap year.");
}else{
printf("Entered year is not a leap year.");
}

return 0;
}
```

We can also simplify the checkLeapYear function as below :

```#include
#define LEAP_YEAR 1
#define NON_LEAP_YEAR 0

int checkLeapYear(int year)
{
if(((year%4==0) && (year%100!=0)) ||(year%400==0)){
return LEAP_YEAR;
}else{
return NON_LEAP_YEAR;
}
}
int main()
{
int year;

printf("Enter a year to check : \n");

scanf("%d",&year);

if(checkLeapYear(year) == LEAP_YEAR){
printf("Entered year is a leap year.");
}else{
printf("Entered year is not a leap year.");
}

return 0;
}
```

Sample Output :

```Enter a year to check :
2018
Entered year is not a leap year.

Enter a year to check :
1984
Entered year is a leap year.

Enter a year to check :
2000
Entered year is a leap year.
```

The output is same for both of these program.